By JEFF DONN
.c The Associated Press
(Nov. 4) - Fossils of fish that wriggled around the seas more than 500
million years ago - about 50 million years before the oldest known
vertebrates to man - have been found in China, researchers say.
The discovery of the 2 1/2-inch fossils suggests that vertebrates - animals
with primitive spines or backbones - had already undergone considerable
evolution by the Cambrian epoch, from about 490 million to 545 million years
ago. Many other major animal groups appear in the fossil record for the first
time during this period of rapid evolution.
Cambridge University scientist Simon Conway Morris said the fishlike fossils
are about 530 million years old, which would put them in the middle of the
Cambrian period.
Up to now, the oldest known vertebrate fossil was about 480 million years
old, or from the end of the Cambrian period.
Morris said the latest find means that ''the so-called Cambrian explosion was
more abrupt and dramatic than we thought.''
However, Desmond Collins, a paleontologist at the Royal Ontario Museum in
Toronto, said it is too soon to say if the history of early evolution must be
rewritten. He pointed out that no similar specimens have been uncovered in
the same area, where tens of thousands of fossils have been removed since the
field was discovered in the early 1900s.
''Why is there so little fossil record?'' he asked.
Two Chinese teams uncovered the two fossils within the past year at the
Chengjiang fossil field. Morris and researchers from China studied the
fossils and reported their findings today in the journal Nature.
They argue that the fossils are clearly early agnathans, a type of jawless
fish that includes the modern lamprey and hagfish. They point to clear signs
of zigzag muscle patterns and gill structures - both characteristics of
modern fish. One fossil shows marks of an early spine.
Philippe Janvier, a paleontologist at the Museum of Natural History, in
Paris, said in a Nature commentary that the new fossils ''are probably the
long-awaited early Cambrian vertebrates.''
The Chinese-British team said the fin-bearing animals would have been active
swimmers, making it less likely they would have been buried alive when storms
stirred up sediment from the bottom of the sea. This may help explain why no
other such animals have been found this early in history.
Morris said the two ancient agnathans appear quite evolved. He suggested that
the first vertebrates must have developed much earlier, perhaps 555 million
years ago or more.
AP-NY-11-04-99 0151EST